The problem of elevator rope and cable sway is well known in the art. In tall buildings elevator ropes and cables, which include hoist ropes, compensation ropes, governor ropes, and traveling cables, are known to vibrate in sympathy with the wind induced sway of the building and other dynamic factors affecting the building. The swaying of the ropes causes many problems chief among them is increased fatigue and wear, excessive noise, and the increased possibility of tangling.
Numerous attempts have been made in the industry to reduce or eliminate elevator rope sway and its detrimental effects on elevator usage. For instance, elevator motion control systems have been employed to control elevator car movement such as inhibiting the dispatching of an elevator car if rope sway is determined to be excessive, prohibiting elevator cars from parking on floors that would enhance sway, reducing elevator car speed when excessive rope sway is detected, and maintaining elevator cars in continues motion to prevent excessive sway conditions. Since elevator hoistway space detracts from useful building space the hoistway dimensions are typically quite small and any attempt at reducing rope sway must fit within a relatively small area.
In another approach, a follower car is positioned below an elevator car and travels along with the elevator car at half the distance between the car and the pit. The follower car effectively creates a node at the midpoint and reduces rope sway. Some of the problems with employing a follower car are that it is relatively expensive, increases the load on the elevator drive machine and hoist ropes, is ineffective for hoist rope swag and also requires an increased pit depth.
In still other approaches guides or poles are placed within the shaft to limit the sway of the ropes. One such approach is disclosed in U.S. Pat. No. 5,103,937 ('937). The '937 patent teaches the use of an oscillation limiting member which mounts to a wall of an elevator hoistway an extends into the hoistway to contact the ropes and thereby limit rope sway. One problem with the apparatus taught in the '937 patent is that the solid members project perpendicular from the walls of the hoistway and must be mounted near the center of the hoistway to be placed proximate the ropes in an extended position. As such the apparatus would interfere with side rails, counter balance weights and rails, as well as other elevator equipment positioned near the center of most elevator hoistway walls. In addition, in the event of a collision between an elevator car and an apparatus as disclosed in the '937 patent the apparatus would break free from the mount and fall to the bottom of the hoistway causing possible structural damage. Another problem with the apparatus disclosed in the '937 patent is that the solid members are heavy and cantilevered from the wall and as such a large amount of torque is required from the actuator to reliably extend and retract the member. This requires a large actuator which may require a larger space than most hoistways allow. The cable members disclosed within the '937 patent also require more space than is typically available in elevator hoistways and are restricted from installation in those quadrants of the hoistway which may be occupied by the governor rope, traveling cables, selector tape, etc.
The rope sway limiting devices of the '937 patent as well as most other devices of the prior art also have the disadvantage of being incapable of retrofit into existing elevator installations. As such there is a need for a reliable and effective device to reduce elevator rope sway which eliminates or reduces the problems of the prior art.